R. Yosef Eliyahu Henkin, Kisvei Ha-Gri Henkin, vol. 2 p. 57:
Regarding Chalav Yisrael: According to the Shulchan Aruch it is a very strict matter. However, since there is an obligation to the government many are lenient, and so it is said in the name of the Chazon Ish. Therefore, even those who are strict, are lenient on the utensils and particularly with family members. Also, butter is more lenient than milk. But if one wishes to be strict he must say “b’li neder” because it relates to issues of vows.
(See also this post)